Mobile communications devices communicate wirelessly with various types of devices, such as base stations, satellites and other wireless devices, using any of a number of wireless protocols using electromagnetic waves as RF signals. In some mobile devices, the RF signal is at ISM-band frequencies, between about 2.400 GHz and about 2.483 GHz (used for IEEE 802.11 Wi-Fi and Bluetooth). In other mobile devices, the RF signal is transmitted at five GHz U-NII band frequencies, between about 4915 MHz and about 5825 MHz (used for Wi-Fi). In other mobile devices, the RF signal is at 1575.42 and 1227.60 MHz (used for GPS). In other mobile devices, the RF signal is at UMTS/LTE band frequencies, which may be about 800 MHz, about 850 MHz, about 900 MHz, about 1500 MHz, about 1700 MHz, about 1800 MHz, about 1900 MHz, or about 2100 MHz. Of course, other frequency bands may be supported by the mobile device. For each frequency band supported by the mobile device, an antenna must be able to transduce the electromagnetic wave into a voltage at a specified impedance.
The mobile device typically has antennas that may be planar or three-dimensional structures distributed with respect to a device housing, e.g., embedded within the mechanical structure of the device. There may be a number of antennas greater than, equal to or less than the number of wireless frequencies and standards supported by the device. A set of antennas may be around the perimeter of the device, on the back, and/or on the front.
Most materials are not RF transparent and will cause diffraction effects. One of the challenges with mobile devices is that human body parts, such as hands and arms, may attenuate the signal produced from a transmitter and/or may attenuate signals transmitted by other devices, e.g., due the absorption/redirection of radio frequency signals on the human body. For example, a hand holding a mobile communication device can affect transmission and reception of wireless communication signals.